You know how a chance whiff of an old lover’s perfume or cologne can send you right back into the agony and the ecstasy of that relationship? Even more homey smells, like your favorite childhood meal, have the ability to seemingly transport you in time, back to being that little kid again. Smell is a powerful sense that goes directly to the core of our emotional brain and it plays a key role in attraction.

Fascinating research shows that a woman’s sense of smell can lead to her to Mr. Right, at least reproductively speaking. Research has shown that each of us will be attracted to people who possess a particular set of genes, known as the major histocompatibility complex (MHC), which play a critical role in our immune systems. Mates with dissimilar MHC genes produce healthier offspring with broad immune systems.

How do people who differ in their MHC find each other? This isn't fully understood, but we know that smell is an important cue. People appear to literally sniff out their mates. In studies, women tend to rate the scent of T-shirts worn by men with dissimilar MHCs as most attractive, whereas T-shirts worn by guys with similar MHC profiles tend to be rated as “fatherly” or “brotherly,” but not boyfriend material. This is what sexual "chemistry" is all about. We’re drawn to certain people, without quite knowing why.

In my own surveys of men and women, women rate scent much more highly than men. This makes sense evolutionarily speaking, since women carry children for nine months during pregnancy and would need to sniff out a good mate who would stick around and support them.

Many women who have satisfying sex lives claim to love the scent of their guy, while many women who have dissatisfying sex claim their guy’s scent does nothing for them, or even turns them off. When I talk to women in relationships who claim that the sexual attraction was never really there to begin with, many also say that they didn’t like, or notice, his smell.

So, ladies, ask yourself: Do you like the way he smells? Does it turn you on? Get you going?

Here are some tips to put the power of smell to work for your sex life — and maybe your future progeny. Remember, if you’re into his smell, it goes a long way toward speaking to chemistry. If you’re not, it could have a negative impact on the relationship.

If you’re wondering if he’s the one, take a good whiff of some of his clothes — how does it make you feel? Do you think warm, fuzzy thoughts or do you think he should really do his laundry? Or, try an overnight with a favorite article of his clothing. Many women love to sleep in their husband’s shirts, wear their men’s sweatshirts and are picking up on the scent, whether it’s conscious or unconscious. Do you like to wear his stuff when he’s not around? It’s another sign along the trail to sniffing out your MHC compatibility.

Take a break from the pill and use another form of birth control. Research shows that the pill may interfere with a woman’s ability to sniff out a compatible mate, since it tricks the body into thinking she’s already pregnant. Some researchers suggest that if you’re single, you should forgo the pill until you’re sure you’ve met your match. Try another form of birth control and see if some scent-awareness appears.

Try some scent-sational aphrodisiacs. A study conducted by the Smell and Taste Research Foundation in Chicago uncovered some powerful smells for boosting his arousal. The scent of lavender and pumpkin pie, and donuts and black licorice, in particular, increased blood flow to the penis by nearly 40 percent! So turn up the volume on an attraction that’s already there with some strategic baking or candles on your next date night at home.

Smell-train your man. Men may not have as keen a sense of smell as women, but it’s still a sense that’s often neglected. One female patient told me that she had a secret. Whenever her husband wanted to have sex, she would go freshen up and put on some perfume. He had become so used to the association of that scent and sex, that when she was in the mood, all she had to do was put some on and he wanted to have sex.

Scent can help fuel the flames of desire — and cool the flames of conflict. When you’re fighting, take a break to “hug and smell” — 20-second hugs raise oxytocin levels (the feel-good chemical) and following your nose will help you put the tension behind you.

So what’s the lesson, ladies? Follow your nose, it always knows!

Ian Kerner is a sex therapist, relationship counselor and New York Times best-selling author of numerous books, including the recently published “Sex Detox: A Program to Detoxify and Rejuvenate Your Love Life.” He was born and raised in New York City, where he lives with his wife, two young sons and plump Jack Russell terrier.

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